1. Field of the Invention
This invention relates to rotors for compressors and turbines and, more specifically, to shear pins mounted between the disks which form the rotor.
2. Background Information
The hub of a compressor or turbine rotor is comprised of a plurality of stacked disks. Each disk provides a means for attaching a plurality of blades. The combination of blades and disks form the bulk of the rotor. The disks are situated one next to another forming a stack with an interface between each pair of disks. The disks may be attached to each other by various means such as a threaded fastener passing axially through each disk. Such fasteners hold the disks axially and assist in creating friction at each interface between the disks. The friction at the interface between each disk transmits engine torque throughout the rotor stack. Additionally, it is known to provide radial shear pins at each disk interface to assist in transmitting engine torque.
Prior art shear pins included a pin body with an expanded portion at both ends. The pins were positioned in holes bored into the rotor stack. The holes extend between the outer surface of the rotor stack and a cavity which is formed between each pair of disks. The holes are counter-bored on each end. Thus, after a pin was installed in a hole, the expanded ends of the pin fit into the counter-bores, preventing the pins from moving radially and securing the pins within the holes during operation or the rotor.
The installation of the prior art shear pins was a time consuming operation. The process entailed a total of two disk stacking and one de-stacking operations. The first stacking operation was required to position the disks to allow the holes to be bored at the interface between each disk. After the holes were bored, the ends were counter-bored, and back counter-bored. Because the pin holes extended into an inner cavity in the rotor, debris from the drilling operation fell into the cavity. The rotor had to be de-stacked to allow removal of the cutting debris and to allow placement of the pins between each rotor disk. Additionally, the bore holes needed to be cleaned and de-burred prior to insertion of the pins between the disks. As each disk was being re-stacked, a plurality of pins were set, one each, in the bore holes on the exposed interface. As the next disk in the stack was put in place, the pins became trapped in the bore holes by virtue of the expanded ends.
There is, therefore, a need for a rotor shear pin that may be installed without requiring the rotor stack to be de-stacked.
There is a further need for a rotor shear pin that may be installed in a blind pin hole.